Curable polyurethanes, coatings prepared therefrom, and method of making the same

ABSTRACT

A polyurethane material, the coatings prepared therefrom, and methods of making the same are provided. An anionic self-crosslinkable polyurethane material has a weight average molecular weight of less than 15,000 grams per mole and, when cured, has a toughness of at least 20 MPa according to TOUGHNESS TEST METHOD at a temperature of 25° C.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims priority from provisional U.S. PatentApplication Serial No. 60/234,514, filed Sep. 22, 2000, and is relatedto U.S. patent application Ser. Nos. 09/611,051 and 09/668,085, filedJul. 6, 2000 and Sept. 22, 2000, respectively, which areContinuations-In-Part of U.S. patent application Ser. No. 09/309,851,filed May 11, 1999, now U.S. Pat. No. 6,248,225B1.

FIELD OF THE INVENTION

[0002] The present invention is directed to a curable polyurethanematerial, coatings prepared therefrom, and methods of making the same.

BACKGROUND OF THE INVENTION

[0003] Coating formulations find use in various industries including thecoating and/or painting of motor vehicles. In these industries, and inthe automotive industry in particular, considerable efforts have beenexpended to develop coating compositions with improved performanceproperties. In the automotive industry, for example, numerous approacheshave been advanced to achieve improved chip resistance and corrosionprotection. These efforts have included, for example, applying up to 6or more individually applied coating layers over the substrate by one ormore coating methods.

[0004] These coatings may be applied by either electrophoretic ornon-electrophoretic coating methods. Electrodeposition has becomeincreasingly important in the coatings industry because, by comparisonwith non-electrophoretic coating means, electrodeposition offers higherpaint utilization, outstanding corrosion protection, low environmentalcontamination, and a highly automated process. Generally, cationicelectrodeposited coatings provide better corrosion resistance thananionic electrodeposited coatings. Non-electrophoretic coatings, such assprayable coatings, however, are still widely used throughout thecoatings industry because of the relatively low equipment and operatingcosts associated therewith.

[0005] Such efforts have resulted in increased protection of the surfaceof the substrate and reduced paint loss through chipping when thesubstrate of the vehicle is hit with solid debris such as gravel andstones. By reducing the difference in impact energy between multiplecoating layers, it is believed that chip resistance of the overallcoating can be improved, especially for coatings in which the respectivecoating layers have excessive differences in hardness. It is believedthat reducing the hardness differential can lessen delamination betweenthe coating layers such as between the undercoat, an intermediate coat,and a topcoat or an undercoat and an intermediate coat.

[0006] In U.S. Pat. No. 5,047,294, this differential is said to bereduced by applying a crosslinked polyurethane resin filler compositionbetween coating layers to improve intercoat adhesion. The fillercomposition includes a water-dispersible polymer derived frompolyisocyanates, high and low molecular weight polyols, compoundsreactive with the isocyanate, and monofunctional or activehydrogen-containing compounds. Anhydrides of carboxylic acids, such astrimellitic acid, are disclosed as useful to form the high molecularweight polyol. The coating formulation is typically applied as anintermediate coat between the primer and the topcoat to even outirregularities present in the primer, and improve the overall stone-chipresistance of the coating.

[0007] In U.S. Pat. No. 5,674,560, a chip resistant polyolefin type ofprimer is spray applied over a cationic or anionic electrodepositedcoated film before application of a soft intermediate polyester film.The reduction of the differential in impact energy is reportedlymaximized when the polyolefin primer is applied over the softer anionicelectrodeposited film as opposed to a cationic electrodeposited film.

[0008] Even though electrophoretic coatings can provide many advantagesover non-electrophoretic coatings, improvements to each are still soughtbecause of the widespread use of both.

[0009] Accordingly, the need exists for a polyurethane material usefulin coating compositions that can and may be applied to the substrate byelectrophoretic and non-electrophoretic coating methods.

SUMMARY OF THE INVENTION

[0010] The present invention provides an anionic self-crosslinkablepolyurethane material, the polyurethane material having a weight averagemolecular weight of less than 15,000 grams per mole, wherein thepolyurethane material, when cured, has a toughness of at least 20 MPaaccording to TOUGHNESS TEST METHOD at a temperature of 25° C.

[0011] In one embodiment, the polyurethane material comprises isocyanatefunctional groups, the isocyanate functional groups blocked with ablocking agent. In another embodiment, the polyurethane material isanionic.

[0012] The present invention is also directed to a primer coatingcomposition, a basecoat composition, a clearcoat composition, a monocoatcomposition, and a multicomponent composite coating including thepolyurethane material described above. Where the present invention is amulticomponent composite composition, at least one of the layerscomprises the polyurethane material.

[0013] The present invention is also directed to a coated substratehaving coated layers applied thereover, at least one of the coatedlayers comprising the polyurethane material of the present invention.

[0014] The present invention is also directed to a process for formingan aqueous composition comprising an anionic self-crosslinkablepolyurethane material, the process comprising:

[0015] (a) forming the polyurethane material, the polyurethane materialhaving a weight average molecular weight of less than 15,000 grams permole, wherein the polyurethane material, when cured, has a toughness ofat least 20 MPa according to TOUGHNESS TEST METHOD at a temperature of25° C.; and

[0016] (b) dispersing the polyurethane material in water to form anaqueous composition.

[0017] The present invention is also directed to a process for preparinga coated substrate, comprising,

[0018] (a) forming a coating on the substrate, the coating being acomposition comprising an anionic self-crosslinkable polyurethanematerial, the polyurethane material having a weight average molecularweight of less than 15,000 grams per mole, wherein the polyurethanematerial, when cured, has a toughness of at least 20 MPa according toTOUGHNESS TEST METHOD at a temperature of 25° C.; and

[0019] (b) at least partially curing the coating.

DETAILED DESCRIPTION OF THE INVENTION

[0020] Other than in the operating examples, or unless otherwiseexpressly specified, all of the numerical ranges, amounts, values andpercentages such as those for amounts of materials, times andtemperatures of reaction, ratios of amounts, values for molecular weight(whether number average molecular weight (“M_(n)”) or weight averagemolecular weight (“M_(w)”)), and others in the following portion of thespecification may be read as if prefaced by the word “about” even thoughthe term “about” may not expressly appear with the value, amount orrange. Accordingly, unless indicated to the contrary, the numericalparameters set forth in the following specification and attached claimsare approximations that may vary depending upon the desired propertiessought to be obtained by the present invention. At the very least, andnot as an attempt to limit the application of the doctrine ofequivalents to the scope of the claims, each numerical parameter shouldat least be construed in light of the number of reported significantdigits and by applying ordinary rounding techniques.

[0021] Notwithstanding that the numerical ranges and parameters settingforth the broad scope of the invention are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contain certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Furthermore, when numerical ranges ofvarying scope are set forth herein, it is contemplated that anycombination of these values inclusive of the recited values may be used.

[0022] Any numeric references to amounts, unless otherwise specified,are “by weight”. The term “equivalent weight” is a calculated valuebased on the relative amounts of the various ingredients used in makingthe specified material and is based on the solids of the specifiedmaterial. The relative amounts are those that result in the theoreticalweight in grams of the material, like a polymer, produced from theingredients and give a theoretical number of the particular functionalgroup that is present in the resulting polymer. The theoretical polymerweight is divided by the theoretical number of equivalents ofurethane/urea groups to give the equivalent weight. For example,urethane/urea equivalent weight is based on the equivalents of urethaneand urea groups in the polyurethane/urea material.

[0023] As used herein, the term “polymer” is meant to refer to oligomersand both homopolymers and copolymers. Also, as used herein, the term“polyurethane material” is meant to include polyurethanes, polyureas,and mixtures thereof.

[0024] Also for molecular weights, whether M_(n) or M_(w), thesequantities are determined by gel permeation chromatography usingpolystyrene as standards as is well known to those skilled in the artand such as is discussed in U.S. Pat. No. 4,739,019 at column 4, lines2-45, which is incorporated herein by reference in its entirety.

[0025] As used herein “based on total weight of the resin solids” of thecomposition means that the amount of the component added during theformation of the composition is based upon the total weight of the resinsolids (non-volatiles) of the film forming materials, polyurethanes,cross-linkers, and polymers present during the formation of thecomposition, but not including any water, solvent, or any additivesolids such as hindered amine stabilizers, photoinitiators, pigmentsincluding extender pigments and fillers, flow modifiers, catalysts, andUV light absorbers.

[0026] As used herein, “formed from” denotes open, e.g., “comprising,”claim language. As such, it is intended that a composition “formed from”a list of recited components be a composition comprising at least theserecited components, and can further comprise other nonrecited componentsduring is the composition's formation.

[0027] As used herein, the term “cure” as used in connection with acomposition, e.g., “a curable polyurethane material”, “a curedcomposition,” shall mean that any crosslinkable components of thecomposition are at least partially crosslinked. In certain embodimentsof the present invention, the crosslink density of the crosslinkablecomponents, i.e., the degree of crosslinking, ranges from 5% to 100% ofcomplete crosslinking. In other embodiments, the crosslink densityranges from 35% to 85% of full crosslinking. In other embodiments, thecrosslink density ranges from 50% to 85% of full crosslinking. Oneskilled in the art will understand that the presence and degree ofcrosslinking, i.e., the crosslink density, can be determined by avariety of methods, such as dynamic mechanical thermal analysis (DMTA)using a TA Instruments DMA 2980 DMTA analyzer conducted under nitrogen.This method determines the glass transition temperature and crosslinkdensity of free films of coatings or polymers. These physical propertiesof a cured material are related to the structure of the crosslinkednetwork.

[0028] The average particle size can be measured according to knownlaser scattering techniques. For example, the average particle size ofsuch particles is measured using a Horiba Model LA 900 laser diffractionparticle size instrument, which uses a helium-neon laser with a wavelength of 633 nm to measure the size of the particles and assumes theparticle has a spherical shape, i.e., the “particle size” refers to thesmallest sphere that will completely enclose the particle.

[0029] As used herein, “TOUGHNESS TEST METHOD” refers to test proceduresfor determining tensile properties of polymeric materials based upon amodified form of ASTM # D 2370-92, entitled “Standard Test Method forTensile Properties of Organic Coatings” (1992), incorporated byreference herein in its entirety. Relative to ASTM # D 2370-92, TheTOUGHNESS TEST METHOD provides for the preparation of flexible coatingsthat are cured at relatively low temperatures (less than about 100° C.)using a non-adhering substrate such as polypropylene, polyvinylfluoride,or Teflon™. A liquid coating is applied to the substrate (spray or wirebar) and is thereafter cured or aged. The coating is then cut into a½″×4″ free film sample size, and peeled from the substrate. But forthese modifications, the TOUGHNESS TEST METHOD” incorporates the sametesting procedures as ASTM # D 2370-92.

[0030] The present invention is directed to a curable polyurethanematerial, coatings prepared therefrom, and methods of making the same.

[0031] The curable polyurethane material may be formed from the reactionproduct of components comprising at least one polyisocyanate, at leastone active hydrogen-containing material, at least one polymericpolyamine, such as a polyoxyalkylene polyamine, at least one materialhaving at least one primary or secondary amino group and at least onehydroxyl group, and at least one acid functional material or anhydridehaving a functional group reactive with isocyanate or hydroxyl groups ofother components from which the polyurethane material is formed.Preferably, the polyurethane material is capable of self-crosslinking,i.e., it contains reactive groups which are capable of reacting witheach other to form a crosslinked network. For example, in one embodimentof the present invention, an isocyanate group and a hydroxyl group arecapable of reacting with each other to form a crosslinked network.

[0032] Suitable polyisocyanates used for preparing the polyurethanematerial include aliphatical, cycloaliphatical, araliphatical, and/oraromatic isocyanates, and mixtures thereof. Preferably, thepolyisocyanate is aliphatic or cycloaliphatic.

[0033] Examples of useful aliphatic and cycloaliphatic polyisocyanatesinclude 4,4-methylenebisdicyclohexyl diisocyanate (hydrogenated MDI),hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI),methylenebis(cyclohexyl isocyanate), trimethyl hexamethylenediisocyanate (TMDI), meta-tetramethylxylylene diisocyanate (TMXDI), andcyclohexylene diisocyanate (hydrogenated XDI). Other aliphaticpolyisocyanates include isocyanurates of IPDI and HDI.

[0034] Examples of suitable aromatic polyisocyanates include tolylenediisocyanate (TDI) (i.e., 2,4-tolylene diisocyanate, 2,6-tolylenediisocyanate or a mixture thereof), diphenylmethane-4,4-diisocyanate(MDI), naphthalene-1,5-diisocyanate (NDI), 3,3-dimethyl-4,4-biphenylenediisocyanate (TODI), crude TDI (i.e., a mixture of TDI and an oligomerthereof), polymethylenepolyphenyl polyisocyanate, crude MDI (i.e., amixture of MDI and an oligomer thereof), xylylene diisocyanate (XDI) andphenylene diisocyanate.

[0035] Polyisocyanate derivatives prepared from hexamethylenediisocyanate, 1-isocyanato-3,3,5-trimethyl-5-isocyanatomethylcyclohexane(“IPDI”), including isocyanurates thereof, and/or4,4′-bis(isocyanatocyclohexyl)methane are suitable.

[0036] The amount of polyisocyanate used to prepare the polyurethanematerial generally ranges from about 10 to about 60 percent by weight,preferably about 20 to about 50 percent by weight, and more preferablyabout 30 to about 45 percent by weight based on total weight of theresin solids used to prepare the polyurethane material.

[0037] The components from which the polyurethane material is formedcomprise at least one active hydrogen-containing material. The term“active hydrogen” means those groups that are reactive with isocyanatesas determined by the Zerewitnoff test as is described in the JOURNAL OFTHE AMERICAN CHEMICAL SOCIETY, Vol. 49, page 3181 (1927). Preferably,the active hydrogens are polyols. Nonlimiting examples of suitableactive hydrogen-containing materials comprise polyols, polyethers,polyesters, polycarbonates, polyamides, polyurethanes, polyureas, andmixtures thereof. Preferably, the active hydrogen-containing materialdoes not include acid functional groups.

[0038] In one embodiment, the active hydrogen-containing material may beone or more low molecular weight polyols such as those having two tofour hydroxyl groups. The weight average molecular weight of the lowmolecular weight polyol is typically less than 3000, and is preferablyless than 700, and may be between 60 and 250 grams per mole. Examples ofsuitable low molecular weight polyols include diols, triols, andtetraols having 1 to 10 carbon atoms such as ethylene glycol,1,2-propylene glycol, 1,4-butanediol, trimethylolpropane (preferred),ditrimethylolpropane, trimethylolethane, glycerol, pentaerythritol andsorbitol. Examples of other low molecular weight polyols are etherpolyols such as diethylene glycol and ethoxylated bisphenol A.

[0039] The low molecular weight polyols can be used in amounts of up toabout 50 percent by weight, and preferably from about 2 to about 50percent based on the total weight of the resin solids used to preparethe polyurethane material.

[0040] In another embodiment, the active hydrogen-containing materialcan comprise one or more active hydrogen-containing material. Thesematerials preferably have an average active hydrogen functionalityranging from about 2 to 8, preferably from about 2 to 4, as determinedby the Zerewitnoff test. The weight average molecular weight of theactive hydrogen-containing material preferably ranges from about 400 to10,000, more preferably from 400 to 3,000 grams per mole.

[0041] The glass transition temperature (Tg) of the activehydrogen-containing material is preferably about −120° C. to about 50°C., and more preferably about 0° C. or less. Polyether polyols andpolyester polyols are preferred. Glass transition temperature (Tg) (°C.)is determined using a Differential Scanning Calorimeter (DSC), forexample a Perkin Elmer Series 7 Differential Scanning Calorimeter, usinga temperature range of about −55° C. to about 150° C. and a scanningrate of about 20° C. per minute. The Tg for many polyethers is availablein the literature. Also helpful in determining the Tg is the Clash-Bergmethod, described in Advances in Polyurethane Technology, Burst et al.,Wiley & Sons, 1968, pages 88ff.

[0042] Examples of polyether polyols include polyalkylene ether(poly(oxyalkylene)) polyols which include those having the followingstructural formula:

[0043] wherein the substituent R is hydrogen or lower alkyl containingfrom 1 to 5 carbon atoms including mixed substituents, m is an integerfrom 1 to 4, preferably 1 or 2, and n is an integer typically rangingfrom 5 to 200. Useful polyether polyols include poly(oxytetramethylene)glycols, such as TERATHANE® 650 (preferred), commercially available fromE. I. du Pont de Nemours and Company, LaPorte, Tex., poly(oxyethylene)glycols, poly(oxy-1,2-propylene) glycols and the reaction products ofethylene glycol with a mixture of 1,2-propylene oxide and ethyleneoxide. These materials are obtained by the polymerization of alkyleneoxides such as ethylene oxide, propylene oxide and tetrahydrofuran.

[0044] Also, polyethers obtained from the oxyalkylation of variouspolyols, for example, diols such as 1,6-hexanediol or higher polyolssuch as trimethylolpropane and sorbitol can be used. One commonlyutilized oxyalkylation method is by reacting a polyol with alkyleneoxide such as ethylene or propylene oxide in the presence of an acidicor basic catalyst in a manner well known to those skilled in the art.

[0045] Examples of other active hydrogen-containing polyethers arepolymeric polyamines such as polyether polyamines. Preferred polyetherpolyamines include polyoxyalkylene polyamines. In the practice of theinvention, where he expression “polyoxyalkylene polyamines” is used,what is intended are polyamines containing both oxyalkylene groups andat least two amine groups, preferably primary amine groups, permolecule.

[0046] An example of a preferred polyoxyalkylene polyamine isrepresented by the following structural formula:

[0047] wherein m can range from 0 to about 50, n can range from about 1to about 50, n′ can range from about 1

[0048] to about 50, x can range from about 1 to about 50, y can rangefrom 0 to about 50 and R₁ through R₆ can be the same or different andcan be independently selected from the group consisting of hydrogen orlower alkyl radicals preferably having about 1 to about 6 carbon atoms.

[0049] Another example of a useful polyoxyalkylene polyamine are thoseof the structure:

[0050] wherein R can be the same or different and is selected fromhydrogen, lower alkyl radicals having from 1 to 6 carbon atoms, and nrepresents an integer ranging from about 1 to about 50, preferably about1 to about 35. Non-limiting examples of preferred polyoxyalkylenepolyamines include polyoxypropylene diamines such as Jeffamine® D-2000(preferred) and Jeffamine® D-400, commercially available from HuntsmanCorporation, Houston, Tex. A number of such other polyoxyalkylenepolyamines are described in more detail in U.S. Pat. No. 3,236,895,column 2, lines 40-72; methods of preparation of the polyoxyalkylenepolyamines are illustrated in the patent in Examples 4, 5, 6 and 8-12 incolumns 4 to 9 thereof; the aforementioned portions of U.S. Pat. No.3,236,895 hereby being incorporated by reference.

[0051] Mixed polyoxyalkylene polyamines can be used, that is, those inwhich the oxyalkylene group can be selected from more than one moiety.Examples include mixed polyoxyethylene-propylenepolyamines such as thosehaving the following structural formula:

[0052] wherein m is an integer ranging from about 1 to about 49,preferably about 1 to about 34, and n is an integer ranging from about 1to about 34 and where the sum of n+m is equal to about 1 to about 50,preferably about 1 to about 35.

[0053] Besides the polyoxyalkylenepolyamines mentioned above,derivatives of polyoxyalkylenepolyols may also be used. Examples ofsuitable derivatives would be aminoalkylene derivatives which areprepared by reacting polyoxyalkylenepolyols such as those mentionedabove with acrylonitrile followed by hydrogenation of the reactionproduct in a manner well known to those skilled in the art. An exampleof a suitable derivative would be polytetramethylene glycolbis(3-aminopropyl(ether)). Other suitable derivatives would have thefollowing structural formula:

[0054] wherein the substituent R is hydrogen or lower alkyl containingfrom 1 to 5 carbon atoms including mixed substituents, m is an integerfrom 1 to 4, preferably 1 or 2, and n is an integer typically rangingfrom 5 to 200.

[0055] For mixed oxyethylene-propylene groups in the polyether segment,it is preferred that the oxypropylene content be at least 60 weightpercent, more preferably at least 70 weight percent, more preferably atleast 80 weight percent based on total weight of the resin solids.

[0056] The polyether segment can be derived from a single type ofpolyether polyol or polyamine or various mixtures thereof. Preferred aremixtures of polyether polyols such as polyoxytetramethylene diol andpolyether polyamines such as polyoxypropylenediamine in weight ratios of0.5:1 to 10:1, preferably 0.5:1 to 7:1, and most preferably 0.6:1.

[0057] Other suitable polyols include polycarbonate diols, polyesterdiols, hydroxyl-containing polydiene polymers, hydroxyl-containingacrylic polymers, and mixtures thereof.

[0058] Examples of polyester polyols and hydroxyl containing acrylicpolymers are described in U.S. Pat. Nos. 3,962,522 and 4,034,017,respectively, which are incorporated herein by reference. Examples ofpolycarbonate polyols are described in U.S. Pat. No. 4,692,383 in col.1, line 58 to col. 4, line 14, which is incorporated herein byreference. Examples of hydroxyl-containing polydiene polymers aredisclosed in U.S. Pat. No. 5,863,646, col. 2, lines 11-54, which isincorporated herein by reference. These polymeric polyols generally canhave a weight average molecular weight ranging from 400 to 10,000 gramsper mole.

[0059] Generally, the amount of active hydrogen-containing material thatis used to prepare the polyurethane is at least about 30 weight percent,preferably at least about 35 weight percent, and more preferably fromabout 35 to about 50 percent by weight based on total weight of theresin solids used to make the polyurethane material.

[0060] The polyisocyanate(s) and active hydrogen-containing material(s)may be added with some or all of the components that form thepolyurethane of the present invention, but preferably are prereactedtogether in a manner well known to those skilled in the art to form aprepolymer prior to reaction with the other components used to preparethe polyurethane material. For example, the polyisocyanate(s) and activehydrogen-containing material(s) may be prereacted at between 40-90° C.using up to about 0.5%, and preferably about 0.04%, dibutyl tindilaurate. Generally, the ratio of isocyanate equivalents to activehydrogen equivalents ranges from 10:1 to 2:1, and more preferably 5.1 to2:1.

[0061] The components from which the polyurethane material is formedcomprise at least one polyamine, preferably a polyoxyalkylene polyaminesuch as are described above. This polyoxyalkylene polyamine can be thesame or different from the polyoxyalkylene polyamine used to prepare theprepolymer above, although preferably it is different. As used herein,with respect to components, “different” means that the respectivecomponents do not have the same chemical structure.

[0062] Other useful polyamines include primary or secondary diamines orpolyamines in which the groups attached to the nitrogen atoms can besaturated or unsaturated, aliphatic, alicyclic, aromatic,aromatic-substituted-aliphatic, aliphatic-substituted-aromatic andheterocyclic. Exemplary suitable aliphatic and alicyclic diaminesinclude 1,2-ethylene diamine, 1,2-porphylene diamine, 1,8-octanediamine, isophorone diamine, propane-2,2-cyclohexyl amine, and the like.Suitable aromatic diamines include phenylene diamines and the toluenediamines, for example, o-phenylene diamine and p-tolylene diamine. Theseand other suitable polyamines are described in detail in U.S. Pat. No.4,046,729 at column 6, line 61 to column 7, line 26, incorporated hereinby reference.

[0063] Based upon the total weight of resin solids from which thepolyurethane material is formed, the amount of polyamine can range fromabout 1 to 40 weight percent, preferably about 5 to about 40 weightpercent, and more preferably about 10 to about 30 weight percent. In oneembodiment, the amount of polyamine present in the polyurethane materialis about 14 weight percent based on the total weight of the resinsolids.

[0064] The components from which the polyurethane material is formedcomprise at least one material having at least one primary or secondaryamino group and at least one hydroxyl group. This material is differentfrom the active hydrogen-containing material component and polyaminecomponent discussed above, i.e., it has a chemically differentstructure. Nonlimiting examples of such materials include primaryamines, secondary amines, diethanolamine, ethanlolamine, N-methylethanolamine, 2-amino-1-propanol, 2-amino-2-methyl-1-propanol,2-amino-2-methyl-1,3-propanediol, diisopropanolamine,2-amino-2-ethyl-1,3-propanediol, tris(hydroxymethyl) amino-methane, andmixtures thereof.

[0065] Based upon the total weight of resin solids from which thepolyurethane material is formed, the amount of material having at leastone primary or secondary amino group and at least one hydroxyl group canrange from about 2 to about 20, and preferably about 3 to about 10weight percent.

[0066] The components from which the polyurethane material is formedcomprise at least one acid functional material or anhydride having afunctional group reactive with the isocyanate or hydroxyl groups ofother components from which the polyurethane material is formed. Usefulacid functional materials include compounds and polymers having thestructure:

X—Y—Z

[0067] wherein X is OH, SH, NH₂, or NHR, and R includes alkyl, aryl,cycloalkyl, substituted alkyl, substituted aryl, and substitutedcycloalkyl groups, and mixtures thereof; Y includes alkyl, aryl,cycloalkyl, substituted alkyl, substituted aryl, and substitutedcycloalkyl groups, and mixtures thereof; and Z includes OSO₃H, COOH,OPO₃H₂, SO₂OH, POOH, and PO₃H₂, and mixtures thereof. Examples ofsuitable acid functional materials include hydroxypivalic acid(preferred), 3-hydroxy butyric acid, D,L-tropic acid, D,L hydroxymalonic acid, D,L-malic acid, citric acid, throglycolic acid, glycolicacid, amino acid, 12-hydroxy stearic acid, mercapto propionic acid,mercapto butyric acid, mercapto-succinic acid, and mixtures thereof.Useful anhydrides include aliphatic, cycloaliphatic, olefinic,cycloolefinic and aromatic anhydrides. Substituted aliphatic andaromatic anhydrides also are useful provided the substituents do notadversely affect the reactivity of the anhydride or the properties ofthe resultant polyurethane. Examples of substituents include chloro,alkyl and alkoxy. Examples of anhydrides include succinic anhydride,methylsuccinic anhydride, dodecenyl succinic anhydride,octadecenylsuccinic anhydride, phthalic anhydride, tetrahydrophthalicanhydride, methyltetrahydrophthalic anhydride, hexahydrophthalicanhydride, alkyl hexahydrophthalic anhydrides such asmethylhexahydrophthalic anhydride, tetrachlorophthalic anhydride,endomethylene tetrahydrophthalic anhydride, trimellitic anhydride(preferred), chlorendic anhydride, itaconic anhydride, citraconicanhydride, maleic anhydride, and mixtures thereof.

[0068] The acid functional material or anhydride provides thepolyurethane material with anionic ionizable groups which can be ionizedfor solubilizing the polymer in water. For the purposes of thisinvention, the term “ionizable” means a group capable of becoming ionic,i.e., capable of dissociating into ions or becoming electricallycharged. The acid is neutralized with base to from a carboxylate saltgroup. Examples of anionic groups include —OSO₃ ⁻, —COO⁻, —OPO₃ ⁼,—SO₂O⁻, —POO⁻; and PO₃ ⁼, with COO⁻being preferred.

[0069] The amount of acid functional material or anhydride that is usedto prepare the polyurethane material is at least about 2 percent,preferably ranging from at least about 3 to about 8 percent, and morepreferably ranging from about 3 to about 4 percent by weight based ontotal weight of the resin solids used to form the polyurethane material.

[0070] The acid groups are neutralized with a base. Neutralization canrange from about 0.1 to about 2.0, preferably about 0.4 to about 1.3, ofthe total theoretical neutralization equivalent. Suitable neutralizingagents include inorganic and organic bases such as sodium hydroxide,potassium hydroxide, ammonia, amines, alcohol amines having at least oneprimary, secondary, or tertiary amino group and at least one hydroxylgroup. Suitable amines include alkanolamines such as monoethanolamine,diethanolamine, dimethylaminoethanol, diisopropanolamine, and the like.The appropriate amount of the neutralizing agent is about 0.1 to about1.0 times, preferably about 0.4 to about 1.0 times the total theoreticalneutralization equivalent.

[0071] The components from which the polyurethane material is formed canfurther comprise at least one polyoxyalkylene polyol. Nonlimitingexamples of suitable polyoxyalkylene polyols include polyoxyethylenepolyols, polyoxypropylene polyols, polyoxybutylene polyols and mixturesthereof. Suitable polyoxyalkylene polyols include, for example,polytetrahydrofuran.

[0072] The amount of polyoxyalkylene polyol that is used to prepare thepolyurethane material is at least about 10 percent, preferably rangingfrom at least about 15 to about 50 percent, and more preferably rangingfrom about to about 40 percent by weight based on total weight of theresin solids used to form the polyurethane material.

[0073] The components can further comprise one or more blocking agentsfor blocking isocyanate functional groups of the polyurethane material.

[0074] Examples of suitable blocking agents used to form thepolyurethane include: oximes, such as acetoxime, methyl ethyl ketoxime,acetophenone oxime, cyclohexanone oxime, and methyl isobutyl ketoxime;carbon-hydrogen acid compounds, such as dialkyl malonate, alkylacetoacetate, and acetylacetone; heterocyclic compounds, such asfurfuryl alcohol, 1,2,4-triazole, and 3,5-dimethylpyrazole; lactams suchas epsilon-caprolactam; amides, such as methyl acetamide, succimide, andacetanilide; phenols, such as methyl-3-hydroxy-benzoate andmethyl-4-hydroxy-benzoate; and amino compounds, such asdiisopropylamine, dicyclohexylamine, di-tert-butylamine, piperidine, and2,2,6,6-tetramethylpiperidine.

[0075] The amount of blocking agent that is used to prepare thepolyurethane material is at least about 5, preferably ranging from atleast about 7 to about 20, and more preferably ranging from about 8 toabout 20 percent by weight based on total weight of the resin solidsused to form the polyurethane material.

[0076] The polyurethane material may be formed by combining theabove-identified components in any suitable arrangement known to one ofordinary skill in the art. For example, in preparing the reactionproducts of the present invention, the components may be combined in asingle step or, as illustrated below, the polyisocyanate and the activehydrogen-containing material may be prereacted under suitable conditionsto form a prepolymer prior to reaction with one or more of the remainingcomponents. Any suitable reaction temperatures may be used to form theprepolymer such as, for example, those reaction temperatures that rangefrom about 50° C. to about 180° C. Next the prepolymer can be furtherreacted with a polyoxyalkylene polyol at any suitable reactiontemperature, such as, for example, about 80° C. Then, a blocking agentmay be reacted therein for blocking at least a portion of isocyanategroups of prepolymer. Such a reaction may be performed at any suitablereaction temperature, such as, for example, about 60° C. to about 90° C.Thereafter, the polyamine material may be added under any suitableconditions, such as, for example at a reaction temperature of about 70°C. to about 75° C., followed by the addition of the material having atleast one primary or secondary amino group and at least one hydroxylgroup under any suitable conditions, such as, for example, at a reactiontemperature of about 60° C. to about 80° C. Then, the acid functionalmaterial or anhydride having a functional group reactive with isocyanateor hydroxyl groups may be reacted therein to form the polyurethanematerial, under suitable conditions, such as, for example, at a reactiontemperature of about 60° C. to about 95° C.

[0077] The polyurethane material can be nonionic, anionic or cationic,but preferably is anionic. The polyurethane will have a weight averagemolecular weight of less than about 15,000 grams per mole, preferablyranging from about 3,000 to about 10,000 grams per mole, and morepreferably ranging from about 4,000 to about 8,000 grams per mole. Themolecular weight of the polyurethane and other polymeric materials usedin the practice of the invention is determined by gel permeationchromatography using a polystyrene standard. The polyurethane also hasactive hydrogen functionality, i.e., hydroxyl, primary or secondaryamine, and typically has an active hydrogen equivalent weight of about500 to about 2500 grams per equivalent, preferably about 800 to about1500 grams per equivalent, and most preferably about 800 to about 1200grams per equivalent. The polyurethane material also may have a combinedurethane/urea equivalent weight ranging from about 200 to about 400grams per equivalent, and mos preferably from about 220 to about 320grams per equivalent. The polyurethane material, when cured, has atoughness of at least about 20 MPa, preferably from about 20 to about 60MPa, and more preferably from about 20 to about 50 MPa.

[0078] One nonlimiting example of the reaction chemistry of oneembodiment of a polyurethane material of the present invention is asfollows:

[0079] The polyurethane material is useful for forming powder, liquid,and powder slurry compositions. Preferably, the polyurethane material ispresent in an aqueous composition.

[0080] The polyurethane material of the present invention may be presentin a composition in the form of an aqueous dispersion. The term“dispersion” is a two-phase transparent, translucent or opaque resinoussystem in which the resin is in the dispersed phase and the water is thecontinuous phase. The average particle size of the resinous phase isgenerally less than 1.0 micron and usually less than 0.5 microns,preferably less than 0.2 micron.

[0081] Generally, the concentration of the resinous phase in the aqueousmedium ranges from about 10 to about 60 percent, and usually about 40 toabout 55 percent, and preferably about 43 to about 55 percent by weightbased on total weight of the aqueous dispersion.

[0082] The composition can further comprise other thermosettablefilm-forming materials, such as polyurethanes which are chemicallydifferent from those discussed above, acrylics, polyesters and epoxyfunctional materials.

[0083] Suitable polyurethane film-forming materials include the reactionproducts of polymeric polyols such as polyester polyols or acrylicpolyols with a polyisocyanate such as are discussed above. Suitableacrylic polymers include polymers of acrylic acid, methacrylic acid andalkyl esters thereof. Other useful film-forming materials and othercomponents for primers are disclosed in U.S. Pat. Nos. 4,971,837;5,492,731 and 5,262,464, which are incorporated herein by reference. Theamount of film-forming material in the composition can range from about30 to about 100 weight percent, and preferably about 40 to about 60weight percent on a basis of total resin solids weight of thecomposition.

[0084] To achieve optimum chip resistance and durability, thepolyurethane material is curable or thermosettable. Preferably, thepolyurethane material is self-crosslinking, although externalcrosslinking agents such as isocyanates blocked with oximes, such asmethyl ethyl ketoxime, or aminoplasts, can be used. Other usefulexternal crosslinking agents include polyisocyanates such as thosedescribed above.

[0085] The polyisocyanate may be fully capped with essentially no freeisocyanate groups and present as a separate component or it may bepartially capped and reacted with hydroxyl or amine groups in thepolyurethane backbone. Examples of suitable polyisocyanates and cappingagents are those described in U.S. Pat. No. 3,947,339, which isincorporated herein by reference in its entirety.

[0086] When the crosslinking agent contains free isocyanate groups, thefilm-forming composition is preferably a two-package composition (onepackage comprising the crosslinking agent and the other comprising thehydroxyl functional polymer) in order to maintain storage stability.Fully capped polyisocyanates are described in U.S. Pat. No. 3,984,299,which is incorporated herein by reference in its entirety.

[0087] The polyisocyanate can be an aliphatic, cycloaliphatic or anaromatic polyisocyanate or a mixture thereof. Diisocyanates arepreferred, although higher polyisocyanates can be used in place of or incombination with diisocyanates. Aliphatic or cycloaliphaticpolyisocyanates are preferred.

[0088] Examples of suitable aliphatic diisocyanates are straight chainaliphatic diisocyanates such as 1,4-tetramethylene diisocyanate and1,6-hexamethylene diisocyanate. Also, cycloaliphatic diisocyanates canbe employed. Examples include isophorone diisocyanate and4,4′-methylene-bis-(cyclohexyl isocyanate). Examples of suitablearomatic diisocyanates are p-phenylene diisocyanate,diphenylmethane-4,4′-diisocyanate and 2,4- or 2,6-toluene diisocyanate.Examples of suitable higher polyisocyanates aretriphenylmethane-4,4′,4″-triisocyanate, 1,2,4-benzene triisocyanate andpolymethylene polyphenyl isocyanate. Biurets and isocyanurates ofdiisocyanates, including mixtures thereof, such as the isocyanurate ofhexamethylene diisocyanate, the biuret of hexamethylene diisocyanate,and the isocyanurate of isophorone diisocyanate are also suitable.

[0089] Isocyanate prepolymers, for example, reaction products ofpolyisocyanates with polyols such as neopentyl glycol and trimethylolpropane or with polymeric polyols such as polycaprolactone diols andtriols (NCO/OH equivalent ratio greater than one) can also be used.

[0090] Any suitable aliphatic, cycloaliphatic, or aromatic alkylmonoalcohol or phenolic compound may be used as a capping agent for thecapped polyisocyanate crosslinking agent in the composition of thepresent invention including, for example, lower aliphatic alcohols suchas methanol, ethanol, and n-butanol; cycloaliphatic alcohols such ascyclohexanol; aromatic-alkyl alcohols such as phenyl carbinol andmethylphenyl carbinol; and phenolic compounds such as phenol itself andsubstituted phenols wherein the substituents do not affect coatingoperations, such as cresol and nitrophenol. Glycol ethers may also beused as capping agents. Suitable glycol ethers include ethylene glycolbutyl ether, diethylene glycol butyl ether, ethylene glycol methyl etherand propylene glycol methyl ether.

[0091] Other suitable capping agents include oximes such as methyl ethylketoxime (preferred), acetone oxime and cyclohexanone oxime, lactamssuch as epsilon-caprolactam, and amines such as dibutyl amine.

[0092] The crosslinking agent may be present in the thermosettingcompositions of the present invention in an amount of at least 1 percentby weight, preferably at least 15 percent by weight, based on totalresin solids weight of the composition and the hydroxy functionalmaterial present. The crosslinking agent is also typically present inthe composition in an amount of less than 60 percent by weight,preferably less than 50 percent by weight, and more preferably less than40 percent by weight, based on total resin solids weight of thecomposition. The amount of crosslinking agent present in thethermosetting composition of the present invention may range between anycombination of these values, inclusive of the recited values.

[0093] The equivalent ratio of hydroxyl groups in the polymer toreactive functional groups in the crosslinking agent is typically withinthe range of 1:0.5 to 1.5, preferably 1.0 to 1.5.

[0094] Aminoplasts are obtained from the reaction of formaldehyde withan amine or amide. The most common amines or amides are melamine, urea,or benzoguanamine, and are preferred. However, condensates with otheramines or amides can be used; for example, aldehyde condensates ofglycoluril, which give a high melting crystalline product that is usefulin powder coatings. While the aldehyde used is most often formaldehyde,other aldehydes such as acetaldehyde, crotonaldehyde, and benzaldehydemay be used.

[0095] The aminoplast contains methylol groups and preferably at least aportion of these groups is etherified with an alcohol to modify the cureresponse. Any monohydric alcohol may be employed for this purposeincluding methanol, ethanol, butanol, isobutanol, and hexanol.

[0096] Preferably, the aminoplasts that are used are melamine-,urea-,glycouril, or benzoguanamine-formaldehyde condensates etherifiedwith an alcohol containing from one to four carbon atoms.

[0097] The aminoplast may be present in the composition in amounts ofabout 5 to about 60, preferably about 15 to about 50 percent by weightbased on the total weight of resin solids.

[0098] The thermosetting composition may also contain catalysts toaccelerate the cure of the crosslinking agent with reactive groups onthe polymer(s). Suitable catalysts for aminoplast cure include acidssuch as acid phosphates and sulfonic acid or a substituted sulfonicacid. Examples include dodecylbenzene sulfonic acid, paratoluenesulfonic acid, and the like. Suitable catalysts for isocyanate cureinclude organotin compounds such as dibutyltin oxide, dioctyltin oxide,dibutyltin dilaurate, and the like. The catalyst is usually present inan amount of about 0.05 to about 5.0 percent by weight, preferably about0.08 to about 2.0 percent by weight, based on the total weight of resinsolids in the thermosetting composition.

[0099] Other ingredients such as pigments and fillers can be present inthe polyurethane composition. Useful pigments include hiding pigmentssuch as titanium dioxide, zinc oxide, antimony oxide, etc. and organicor inorganic UV opacifying pigments such as iron oxide, transparent redor yellow iron oxide, carbon black, phthalocyanine blue, and the like.Useful fillers include barium sulfate, magnesium silicate, calciumcarbonate, and silica. Fillers and pigments can be present in amounts ofup to 60 parts by weight or less based on 100 parts by weight of totalsolids of the composition.

[0100] Other optional ingredients include anti-oxidants, UV-absorbersand hindered amine light stabilizers, such as for example, hinderedphenols, benzophenones, benzotriazoles, triazoles, triazines, benzoates,piperidinyl compounds and mixtures thereof. These ingredients aretypically added in amounts up to about 2 percent based on the totalweight of resin solids of the composition. Other optional ingredientsinclude co-solvents, coalescing aids, defoamers, plasticizers,associative thickeners, bactericides and the like.

[0101] Most electroconductive substrates, especially metal substratessuch as steel, zinc, aluminum, copper, magnesium, or the like andgalvanized metals such as any galvanized steels and the like whether hotdip galvanized or electrogalvanized or other galvanizing method can becoated with the electrodepositable compositions. Steel substrates arepreferred. It is customary to pretreat the substrate with a phosphateconversion coating, usually a zinc phosphate conversion coating,followed by a rinse that seals the conversion coating. Pretreatments arewell known to those skilled in the art. Examples of suitablepretreatment compositions are disclosed in U.S. Pat. Nos. 4,793,867 and5,588,989, which are incorporated herein by reference in their entirety.

[0102] In a preferred embodiment, the coating composition can bedeposited upon a substrate or over an existing coating bynonelectrophoretic means such as spray application, which will bediscussed in detail below.

[0103] It is contemplated that depending upon the desired applicationand use the polyurethane compositions of the present invention may beincorporated into any liquid coating composition, powder coatingcomposition, or aqueous slurry coating composition. As describedhereinbelow, the percent solids of the polyurethane material present inthe coating composition and the thickness of the polyurethanecomposition as applied to the substrate can vary based upon such factorsas the particular coating that uses the polyurethane material of thepresent invention, i.e. whether the polyurethane material is used in aprimer coating, basecoat, clearcoat, topcoat, or combinations thereof,or monocoat composition; and the type of substrate and intended use ofthe substrate, i.e. the environment in which the substrate is placed andthe nature of the contacting materials.

[0104] In addition, it is contemplated that the polyurethane materialcomposition of the present invention may be incorporated into one ormore coating compositions to form a multicomponent composite coating forapplication over a substrate. For example, in one embodiment of thepresent invention, the present invention may be a multicomponentcomposite coating comprising a primer deposited from a primer coatingcomposition and a topcoat applied over at least a portion of the primerin which the topcoat is deposited, wherein at least one of the primercomposition and the topcoat composition comprise the polyurethanematerial of the present invention. In another embodiment of the presentinvention, the present invention may be a multicomponent compositecoating comprising a basecoat deposited from a pigmented coatingcomposition and a clearcoat applied over at least a portion of thebasecoat, the clearcoat being deposited from a clearcoating composition,wherein at least one of the basecoat composition and the clearcoatingcomposition comprise the polyurethane material of the present invention.

[0105] The composition of the present invention may be applied onto thesurface of the substrate or over a polymeric underlayer by any suitablecoating process known to those of ordinary skill in the art, forexample, by dip coating, direct roll coating, reverse roll coating,curtain coating, spray coating, brush coating, electrostatic spraycoating, and combinations thereof. The method and apparatus for applyingthe coating composition to the substrate is determined in part by theconfiguration and type of substrate material. In this regard, thecoatings of the present invention may be applied over either metal orplastic substrates by these application methods. When applied over aplastic substrate, the compositions of the present invention are atleast partially cured at a temperature below the thermal deformationtemperature of the plastics.

[0106] For example, the polyurethane composition employed in aprimer/topcoat composite in a wet-on-wet application. In this example,the polyurethane material may be incorporated into one or both of theprimer and topcoat layers. The following example is provided by way ofillustration only, as one of ordinary skill in the art will recognizethat the polyurethane material-containing composition may, but need not,be applied in a wet-on-wet application, and that other coatings, such aspowder coatings, and coating methods may be employed.

[0107] A substantially uncured coating of the primer coating compositionis formed on the surface of the substrate during application of theprimer coating composition to the substrate. In a preferred embodiment,the surface of the substrate is pretreated as discussed above andelectrocoated with about 20 to about 50 microns of electrodepositioncoating, which is commercially available from PPG Industries, Inc. Othersuitable electrodepositable coatings include those disclosed in U.S.Pat. Nos. 4,891,111; 4,933,056 and 5,760,107, which are herebyincorporated by reference in their entirety.

[0108] The primer composition can be a waterborne coating orsolventborne coating for wet-on-wet application, as desired, but ispreferably a waterborne coating. The primer coating composition maycontain the polyurethane material of the present invention or may be aconventional primer coating composition as described, for example, inU.S. Pat. Nos. 5,126,393; 5,280,067; 5,297,665; 5,589,228 and 5,905,132,which are incorporated herein by reference in their entirety. When theprimer composition contains the polyurethane material of the presentinvention, the percent solids of the polyurethane in the primercomposition may range from about 5 to about 100 percent, and istypically about 20 to about 100 percent by weight based on total weightof the resin solids of the primer composition.

[0109] The primer composition can be applied to the surface of thesubstrate by any suitable coating process known to those of ordinaryskill in the art, for example, by dip coating, direct roll coating,reverse roll coating, curtain coating, spray coating, brush coating,electrostatic spray coating, and combinations thereof.

[0110] A substantially uncured primer coating is formed duringapplication of the primer. As used herein, “substantially uncured”coating means that the coating composition, after application to thesurface of the substrate, forms a film or coating that is substantiallyuncrosslinked, i.e., is not heated to a temperature sufficient to inducesignificant crosslinking and there is substantially no chemical reactionbetween the thermosettable dispersion and the crosslinking material.

[0111] During application of the primer coating composition to thesubstrate, ambient relative humidity generally can range from about 30to about 90 percent, preferably about 60 percent to 80 percent.

[0112] After application of the aqueous primer coating composition tothe substrate, the primer coating can be at least partially dried byevaporating water and solvent (if present) from the surface of the filmby air drying at ambient (about 25° C.) or an elevated temperature for aperiod sufficient to dry the film but not significantly crosslink thecomponents of the primer coating. The heating is preferably only for ashort period of time sufficient to ensure that a topcoat composition canbe applied over the primer coating essentially without dissolving theprimer coating. Suitable drying conditions will depend on the componentsof the primer coating and on the ambient humidity, but in general adrying time of about 1 to about 5 minutes at a temperature of about 80°F. to about 250° F. (about 20° C. to about 121° C.) will be adequate toensure that mixing of the primer coating and the topcoat composition isminimized.

[0113] Preferably, the drying temperature ranges from about 20° C. toabout 80° C., and more preferably about 20° C. to about 50° C. Also,multiple primer coating compositions can be applied to develop theoptimum appearance. Usually between coats, the previously applied coatis flashed; that is, exposed to ambient conditions for about 1 to 20minutes.

[0114] Typically, the coating thickness of the primer coating afterfinal drying and curing of the multilayer composite coating ranges fromabout 0.4 to about 2 mils (about 10 to about 50 micrometers), andpreferably about 1.0 to about 1.5 mils (about 25 to about 38micrometers).

[0115] A topcoat composition is applied to at least a portion of asurface of the primer coating in a wet-on-wet application withoutsubstantially curing the primer coating. The topcoat composition maycontain the polyurethane material of the present invention or may be aconventional topcoat coating composition as described, for example, inU.S. Pat. Nos. 4,403,003; 4,978,708; 5,071,904; 5,368,944; 5,739,194;5,667,847 and 6,093,497, which are incorporated herein by reference intheir entirety. Other suitable compositions are those formulationscommercially available by PPG Industries, Inc. under the tradename HWBand DWB. When the topcoat composition contains the polyurethane materialof the present invention, the percent solids of the polyurethane in thetopcoat composition may range from about 5 to about 100 percent, and istypically about 50 to about 95 percent by weight based on total weightof the resin solids of the topcoat composition.

[0116] The topcoat composition can be a waterborne coating orsolventborne coating for wet-on-wet application, as desired, but ispreferably a waterborne coating. The topcoat may be a monocoat or asystem incorporating a basecoat plus clearcoat, which is preferred.

[0117] The following example illustrates the polyurethane materialemployed in a basecoat/clearcoat composite in a wet-on-wet application.As discussed above, the following example is provided by way ofillustration only, as one of ordinary skill in the art will recognizethat the polyurethane composition may, but need not, be applied in awet-on-wet application, and that other coatings, such as powdercoatings, and coating methods may be employed.

[0118] A substantially uncured coating of the basecoat composition isformed onto the substrate during application of the basecoat compositionto the substrate. The basecoat composition may contain the polyurethanematerial of the present invention or may be a conventional basecoatcomposition as described above. When the basecoat composition containsthe polyurethane material of the present invention, the percent solidsof the polyurethane in the primer composition may range from about 5 toabout 100, and is typically about 40 to about 80 percent by weight basedon the total weight of the resin solids of the basecoat composition.Preferably, the basecoat composition is a crosslinkable coatingcomprising at least one thermosettable film-forming material and atleast one crosslinking material, although thermoplastic film-formingmaterials such as polyolefins can be used. The preferred basecoatcomposition is set forth below in Example 10. Other suitable basecoatsthat may be employed in the present invention are those disclosed inU.S. Pat. No. 5,071,904, which is incorporated herein by reference inits entirety.

[0119] Suitable resinous binders for organic solvent-based basecoats aredisclosed in U.S. Pat. No. 4,220,679 at column 2, line 24 through column4, line 40 and U.S. Pat. No. 5,196,485 at column 11, line 7 throughcolumn 13, line 22. Suitable waterborne base coats for color-plus-clearcomposites are disclosed in U.S. Pat. No. 4,403,003, and the resinouscompositions used in preparing those base coats can be used in thepresent invention. Also, waterborne polyurethanes such as those preparedin accordance with U.S. Pat. No. 4,147,679 can be used as the resinousbinder in the basecoat. Further, waterborne coatings such as thosedescribed in U.S. Pat. No. 5,071,904 can be used as the basecoat. Eachof the patents discussed above is incorporated by reference herein ittheir entirety. Other useful film-forming materials for the basecoatcoating composition include the hydrophobic polymers and/or reactionproduct (a) discussed above. Other components of the basecoatcomposition can include crosslinking materials and additionalingredients such as pigments discussed above. Useful metallic pigmentsinclude aluminum flake, bronze flakes, coated mica, nickel flakes, tinflakes, silver flakes, copper flakes and combinations thereof. Othersuitable pigments include mica, iron oxides, lead oxides, carbon black,titanium dioxide and talc. The specific pigment to binder ration canvary widely so long as it provides the requisite hiding at the desiredfilm thickness and application solids.

[0120] The basecoat composition may be applied to the surface of thesubstrate by any suitable coating process known to those of ordinaryskill in the art, for example, by dip coating, direct roll coating,curtain coating, spray coating, brush coating, electrostatic spraycoating, and combinations thereof. During application of the basecoatcomposition to the substrate, ambient relative humidity generally canrange from about 30 to about 90 percent, preferably about 60 percent to80 percent.

[0121] A substantially uncured basecoat is formed during application ofthe basecoat. Typically, the basecoating thickness after curing of thesubstrate having the multilayered composite coating thereon ranges fromabout 0.4 to about 2.0 mils (about 10 to about 50 micrometers), andpreferably about 0.5 to about 1.2 mils (about 12 to about 30micrometers). Some migration of coating materials between the coatinglayers, preferably less than about 20 weight percent, can occur.

[0122] After application of the basecoat composition to the substrate,the basecoat can be at least partially dried by evaporating water and/orsolvent from the surface of the film by air drying at ambient (about 25°C.) or an elevated temperature for a period sufficient to dry the filmbut not significantly crosslink the components of the basecoatcomposition. The heating is preferably only for a short period of timesufficient to ensure that a clear coating composition can be appliedover the basecoat coating essentially without dissolving the basecoatcoating. Suitable drying conditions depend on the components of thebasecoat composition and on the ambient humidity, but generally thedrying conditions are similar to those discussed above with respect tothe primer coating. Also, multiple basecoat coating compositions can beapplied to develop the optimum appearance. Usually between coats, thepreviously applied coat is flashed; that is, exposed to ambientconditions for about 1 to 20 minutes.

[0123] A clear coating composition is then applied to at least a portionof the basecoat without substantially curing the basecoat coating toform a substantially uncured basecoat/clearcoat composite coatingthereon. When the clear coating composition contains the polyurethanematerial of the present invention, the percent solids of thepolyurethane in the clear coating composition may range from about 5 toabout 100, and is typically about 50 to about 95 percent by weight. Theclear coating composition can be applied to the surface of the basecoatcoating by any of the coating processes discussed above for applying thebasecoat composition.

[0124] The clearcoat composition can be a waterborne coating orsolventborne coating for wet-or-wet application, as desired. Where theclearcoat composition contains the polyurethane material of the presentinvention, the clearcoat composition is preferably a waterborne coating.Preferably the clear coating composition is a crosslinkable coatingcomprising at least one thermosettable film-forming material and atleast one crosslinking material, although thermoplastic film-formingmaterials such as polyolefins can be used. Suitable conventionalwaterborne clearcoats are disclosed in U.S. Pat. No. 5,098,947,incorporated herein by reference in its entirety, and are based on watersoluble acrylic resins. Useful solvent borne clearcoats are disclosed inU.S. Pat. Nos. 5,196,485 and 5,814,410, incorporated herein by referencein their entirety, and include polyepoxides and polyacid curing agents.(Suitable conventional powder clearcoats are described in U.S. Pat. No.5,663,240, incorporated herein by reference in their entirety, andinclude epoxy functional acrylic copolymers and polycarboxylic acidcrosslinking agents.) The clear coating composition can includecrosslinking materials and additional ingredients such as are discussedabove but not pigments.

[0125] During application of the clear coating composition to thesubstrate, ambient relative humidity generally can range from about 30to about 90 percent, preferably about 60 percent to about 80 percent.

[0126] After application of the clear coating composition to thesubstrate, the composite coating can be at least partially dried byevaporating water and/or solvent from the surface of the film by airdrying at ambient (about 25° C.) or an elevated temperature for a periodsufficient to dry the film. Preferably, the clear coating composition isdried at a temperature and time sufficient to crosslink thecrosslinkable components of the composite coating. Suitable dryingconditions depend on the components of the clear coating composition andon the ambient humidity, but generally the drying conditions are similarto those discussed above with respect to the primer coating. Also,multiple clear coating compositions can be applied to develop theoptimum appearance. Usually between coats, the previously applied coatis flashed; that is, exposed to ambient conditions for about 1 to 20minutes.

[0127] A substantially uncured coating of the clearcoat/basecoatcomposite or the topcoat/primer composite is formed on the surface ofthe substrate during application. Typically, the coating thickness aftercuring of the multilayered basecoat/clearcoat composite coating on thesubstrate ranges from about 0.5 to about 4 mils (about 15 to about 100micrometers), and preferably about 1.2 to about 3 mils (about 30 toabout 75 micrometers).

[0128] After application of the clearcoating or topcoating composition,the composite coating coated substrate is heated to cure the coatingfilms or layers. In the curing operation, water and/or solvents areevaporated from the surface of the composite coating and thefilm-forming materials of the coating films are crosslinked. The heatingor curing operation is usually carried out at a temperature in the rangeof from about 160° F. to about 350° F. (about 71° C. to about 177° C.)but if needed, lower or higher temperatures can be used as necessary toactivate crosslinking mechanisms. The thickness of the dried andcrosslinked composite coating is generally about 0.2 to 5 mils (5 to 125micrometers), and preferably about 0.4 to 3 mils (10 to 75 micrometers).

[0129] In one embodiment, compositions including the polyurethanematerial of the present invention may be used for electrodepositioncoating. Such compositions can include an electroconductive pigment tomake the resultant coating electroconductive upon curing. Suitableelectroconductive pigments include electrically conductive carbon blackpigments. Generally, the carbon blacks can be any one or a blend ofcarbon blacks ranging from those that are known as higher conductivecarbon blacks, i.e. those with a BET surface area greater than 500m²/gram and DBP adsorption number (determined in accordance with ASTMD2414-93) of 200 to 600 ml/100 g. to those with lower DBP numbers on theorder of 30 to 120 ml/100 gram such as those with DBP numbers of 40 to80 ml/100 grams.

[0130] Examples of commercially available carbon blacks include CabotMonarch™ 1300, Cabot XC-72R, Black Pearls 2000 and Vulcan XC 72 sold byCabot Corporation; Acheson Electrodag™ 230 sold by Acheson Colloids Co.;Columbian Raven™ 3500 sold by Columbian Carbon Co.; and Printex™ XE 2,Printex 200, Printex L and Printex L6 sold by DeGussa CorporationPigments Group. Suitable carbon blacks are also described in U.S. Pat.No. 5,733,962, which is incorporated herein by reference in itsentirety.

[0131] Also, electrically conductive silica pigments may be used.Examples include “Aerosil 200” sold by Japan Aerosil Co., Ltd., and“Syloid 161”, “Syloid 244”, “Syloid 308”, “Syloid 404” and “Syloid 978”made by Fuji Davison Co., Ltd. Mixtures of different electroconductivepigments can be used.

[0132] The amount of electroconductive pigment in the composition canvary depending on specific type of pigment that is used, but the levelneeds to be effective to provide an electrodeposited coating with aconductivity of greater than or equal to 10⁻¹² mhos/cm. Stated anotherway the electrodeposited coating should have a resistivity of less thanor equal to 10¹² ohms-cm., preferably a resistance of less than or equalto 10⁸ ohms at typical film builds or thicknesses for electrodepositedcoatings. This level is necessary so that upon curing or partial curingthe coating becomes electroconductive. Preferably, curing is by heatingat a temperature of at least 120° C. (248° F.). Typically, theelectroconductive pigment content in the electrodepositable compositionis from 5 to 25 percent by weight based on total solids of theelectrodeposition composition.

[0133] In the process of applying the electrically conductive coating,the aqueous dispersion of the electrodepositable composition is placedin contact with an electrically conductive anode and cathode. Uponpassage of an electric current between the anode and cathode, anadherent film of the electrodepositable composition will deposit in asubstantially continuous manner on either the anode or the cathodedepending on whether the composition is anionically or cationicallyelectrodepositable. Electrodeposition is usually carried out at aconstant voltage in the range of from about 1 volt to several thousandvolts, typically between 50 and 500 volts. Current density is usuallybetween about 1.0 ampere and 15 amperes per square foot (10.8 to 161.5amperes per square meter).

[0134] Furthermore, a second electrodepositable coating that may, butneed not, contain the polyurethane material of the present invention,may be applied over the first electrodeposition coating, describedabove, under the processing conditions described herein in order toprovide a multiple layer electrodeposited coating.

[0135] After electrodeposition, the coating is at least partially cured,typically by heating. Temperatures usually range from about 200° F. toabout 400° F. (about 93° C. to about 204° C.), preferably from about250° F. to 350° F. (about 121° C. to about 177° C.) for a period of timeranging from 10 to 60 minutes. The thickness of the resultant film isusually from about 10 to 50 microns.

[0136] The heating or baking of the electrodeposited coating can also beperformed by means of infrared radiation (“IR”). Generally, there arethree categories of IR. These categories are: near-IR (short wavelength)having a peak wavelength from 0.75 to 2.5 microns (“u”) (750 to 2500nanometers); intermediate-IR (medium wavelength) having a peakwavelength from 2.5 to 4 u (2500 to 4000 nanometers), and far-IR (longwavelength) having a peak wavelength from 4 to 1000 u (4000 to 100,000nanometers). Any or any combination or all of these categories of IR canbe used for the heating to at least partially cure the coating.

[0137] Curing can be done in a selective manner. At least onepredetermined area of the first electrodeposited coating composition isselectively heated by IR, for example, the exterior surfaces of anautomobile body, where such predetermined area is to be coated with thesecond electrodepositable coating composition. The interior surfaces ofthe electrocoated substrate are not exposed to the IR and as a result,the first electrocoat coating is not cured on the interior surfaces anddoes not become electroconductive. Hence the deposition of the secondelectrodeposited coating layer is only on the exterior surfaces whichare electrically conductive. With this treatment, substrates like anautomobile body have the cured, conductive, first electrodepositedcoating on exterior surfaces and the uncured, nonconductive, firstelectrodeposited coating on interior surfaces. Upon application of thesecond electrodeposited coating and curing of both electrodepositedcoatings, the exterior surface of the automobile body will have both thefirst and second electrodeposited coatings and good corrosion and chipresistance where it is needed most. The interior surface will only havethe first electrodeposited coating and corrosion resistance but no chipresistance. Since the interior surfaces will not be exposed to roaddebris, chip resistance is not needed.

[0138] When IR heating is used with complex shapes such as automobilebodies, it is preferable to dry the substrate coated with the firstelectrodeposited coating composition for 2 to 20 minutes, in a standardoven such as a convection, electric, or gas fired oven before exposingthe electrocoated substrate to IR. The drying step can be at atemperature sufficient to remove water but not sufficient to cure thecoating such that it becomes conductive. Generally, the temperature isless than 120° C.

[0139] IR heating can be conducted from 10 seconds to 2 hours, usuallyfrom 5 to 20 minutes. Temperatures range from greater than 120° C. to220° C. (248° F. to 428° F.) and preferably from 130° C. to 190° C.(266° F. to 374° F.).

[0140] The aqueous cationic or anionic polyurethane dispersions aretypically electrodeposited on the electroconductive coating from anelectrodeposition bath having a solids content of 5 to 50 percent byweight. The bath temperature is usually about 15° C. to 35° C. Thevoltage is from 100 to 400 V (load voltage) using the substrate with theelectroconductive coating as a cathode in the case of the cationicpolyurethane or as an anode in the case of the anionic polyurethane. Thefilm thickness of the electrodeposited coating is not particularlyrestricted and can vary largely depending upon the application offinished product, etc. However, the thickness is usually between 3 to 70microns, particularly 15 to 35 microns in terms of cured film thickness.The baking and curing temperature of the coating film is usually from100° C. to 250° C. and preferably 140° C. to 200° C. As mentioned abovein the case of the selective application of the second electrocoatthrough use of the IR bake of the first electrodeposited coating, theheating or baking after application of the second electrocoat can cureboth the first and second electrocoats on surfaces not exposed to IRheating or baking. Also, the baking can complete the cure of the firstelectrocoat that was exposed to IR and overcoated with the secondelectrocoat.

[0141] The invention will further be described by reference to thefollowing examples. The following examples are merely illustrative ofthe invention and are not intended to be limiting. Unless otherwiseindicated, all parts are by weight.

EXAMPLES

[0142] The preparation and physical property evaluation of anionicpolyurethane materials and coatings including the same are described inthe Examples below.

Example 1

[0143] Hydroxy and Blocked Isocyanate Functional Polyurethane Synthesis

[0144] A polyurethane material with both hydroxyl and blocked isocyanatefunctionality according to the present invention was prepared asfollows:

[0145] A reaction vessel equipped with a stirrer, a thermocouple, acondenser, and a nitrogen inlet was charged with 2454.5 g of isophoronediisocyanate, 739.9 g of methyl isobutyl ketone and 1.13 g of dibutyltin dilaurate and heated to 45° C. The isocyanate equivalent wasdetermined from an sample of dibutylamine solution in methylpyrrolidone. Excess dibutylamine was titrated with 0.2 N hydrochloricacid in isopropanol. 134.8 g of trimethylolpropane was added and thereaction was allowed to exotherm to 76° C. After cooling the reactantsto 65° C., another 134.8 g of trimethylolpropane was added to thereaction vessel. The reaction exothermed to 89° C. The reaction productwas allowed to cool to 75° C. After one hour, the isocyanate equivalentweight of the reaction was determined to be 212.7 grams per isocyanateequivalent.

[0146] 1432.7 g of polytetramethyl glycol (as TERATHANE® 650) was addedover one hour followed by 217.5 g of methyl isobutyl ketone. After 30minutes, the isocyanate equivalent weight of the resulting reactionproduct was 438.4 grams per equivalent. Then 557.6 g of methyl ethylketoxime was added over 30 minutes followed by 362.5 g of methylisobutyl ketone. The reaction was stirred for 30 minutes and theisocyanate equivalent weight was 1198.1 grams per equivalent. Thestirring rate was increased to 500 rpm, the reaction temperaturedecreased to 70° C. and 875.6 g of polyoxypropylenediamine (as JeffamineD-2000) was added over two minutes. After stirring an additional 15minutes, 411.9 g of diethanol amine and 72.5 g of methyl isobutyl ketonewere added. The reaction temperature increased to 89° C. The reactioncontents were stirred for about 30 minutes until no evidence ofisocyanate was observed by FTIR. Then 195.8 g of trimellitic anhydridewere added to the reaction flask and the contents stirred for about 4hours until no anhydride was observed by FTIR and only a few flakes oftrimellitic anhydride were observed in the resin. Then, 7.7 g of2-(2H-Benzotriazol-2-yl)-4,6-bis(1-methyl-1-phenylethyl)phenol (asTinuvin 900, commercially available from Ciba Specialty ChemicalsCorporation, Tarrytown, N.Y.), 7.7 g of Decanedioic acid,bis(2,2,6,6-tetramethyl-4-piperidinyl)ester, reaction products with1,1-dimethylethylhydroperoxide and octane (as Tinuvin 123, commerciallyavailable from Ciba Specialty Chemicals Corporation, Tarrytown, N.Y.)and 15.4 g of methyl isobutyl ketone were added to the reactioncontents.

[0147] The resultant product had a solids content of 81.7 weight percent(measured for one hour at 110° C.), an acid value of 15.91 mg KOH/g ofproduct, a hydroxyl value of 57.9 mg KOH/g of product and a weightaverage molecular weight of 4485 g/mole, as determined by gel-permeationchromatography (“GPC”).

Example 2

[0148] Preparation of Aqueous Dispersion of Hydroxyl and BlockedIsocyanate Polyurethane

[0149] 1806.4 g of the polyurethane of Example 1 was heated to 74° C.and added over 43 minutes to a solution of 824.7 g of deionized waterand 45.6 g of dimethyl ethanol amine at 24° C. stirring at 510 rpm in agallon sized cylindrical reaction flask equipped with baffles, a doublepitched bladed stirrer, commercially available from Saxon ResearchSystems, Inc, Saxonburg, Pa., a thermocouple, and a condenser. Thetemperature of the resulting dispersion was 42° C. The dispersion wasstirred for 30 minutes while increasing the dispersion temperature to50° C. Then, the dispersion temperature set point was lowered to 38° C.and 267.7 g of deionized water was added over 20 minutes. The dispersionwas stirred for an additional 45 minutes; another 401.1 g of deionizedwater was added over 25 minutes and the final dispersion stirred foranother 45 minutes.

[0150] This dispersion was transferred to a flask equipped with astirrer, thermocouple, and a spiral condenser with water recoveryreceiver. The dispersion was heated to 60° C. and the methyl isobutylketone removed by vacuum distillation.

[0151] The final dispersion has a solids content of 47.1 weight percent(measured for one hour at 110° C.), a Brookfield viscosity of 411centipoise using a #2 spindle at 30 rpm, an acid content of 0.151 meqacid/g (determined by titration with methanolic potassium hydroxide), abase content of 0.163 meq base/g (determined by titration with 0.2 N HClin isopropanol), a pH of 8.84 (as determined by a pH meter), a residualmethyl isobutyl ketone content of 0.21 weight percent (as determined bygas chromatography), a number average particle size of 1890 angstromsand a volume average particle size of 2020 angstroms (as determined byHoriba Model LA 900 laser diffraction particle size instrument).

Example 3

[0152] Synthesis of Hydroxy and Blocked Isocyanate FunctionalPolyurethane Blocked with 3,5-Dimethyl Pyrazole

[0153] This example illustrates the preparation of a polyurethanematerial using a different isocyanate blocking group(3,5-dimethylpyrazole) than in Example 1.

[0154] A reaction vessel equipped with a stirrer, a thermocouple, acondenser, and a nitrogen inlet was charged with 1269.6 g of isophoronediisocyanate, 382.7 g of methyl isobutyl ketone and 0.59 g of dibutyltin dilaurate and heated to 45° C. 69.8 g of trimethylolpropane wasadded and the reaction was allowed to exotherm to 71° C. After coolingthe reaction to 65° C., another 69.8 g of trimethylolpropane was addedto the reaction flask. The temperature of the reaction product increasedto 89° C. The reaction product was allowed to cool to 75° C. After onehour, the isocyanate equivalent weight of the reaction was 216.9 gramsper isocyanate equivalent.

[0155] 741.1 g of TERATHANE® 650 was added over one hour followed by112.5 g of methyl isobutyl ketone. After 30 minutes, the isocyanateequivalent weight of the reaction was 443.6 grams per equivalent. Then318.6 g of 3,5-dimethyl pyrazole (available from Clariant InternationalLtd., Muttenz, Switzerland) was added in three equal portions over 30minutes followed by 187.5 g methyl isobutyl ketone. The reaction wasstirred for 30 minutes and the isocyanate equivalent weight was 1213.3grams per equivalent. The stirring rate was increased to 500 rpm, thereaction temperature decreased to 70° C. and 453.0 g of Jeffamine D-2000was added rapidly over two minutes. After stirring an additional 15minutes, 213.0 g of diethanol amine and 37.5 g of methyl isobutyl ketonewere added. The temperature of the reactant product was increased to 89°C. The reaction product was stirred until no evidence of isocyanate wasobserved by FTIR. Then 101.3 g of trimellitic anhydride were added tothe reaction flask and the contents stirred until no anhydride wasobserved by FTIR and only a few flakes of trimellitic anhydride wereobserved in the resin. Then 4.0 g of Tinuvin 900, 4.0 g of Tinuvin 123,and 8.0 g of methyl isobutyl ketone were added to the reaction contents.

[0156] The resultant product had a solids content of 80.8 weight percent(measured for one hour at 110° C.), an acid value of 15.56 mg KOH/gproduct, a hydroxyl value of 56.3 mg KOH/g product and a weight averagemolecular weight of 4154 g/mole.

Example 4

[0157] Preparation of Aqueous Dispersion of the Hydroxyl and BlockedIsocyanate Polyurethane of Example 3

[0158]1806.4 g of the polyurethane of Example 3 at 74° C. were addedover 31 minutes to a solution of 825.7 g of deionized water and 44.6 gof dimethyl ethanol amine stirring at 25° C. at 523 rpm in a gallonsized cylindrical reaction flask equipped with baffles, a double pitchedbladed stirrer, a thermocouple, and a condenser. The temperature of theresulting dispersion was 44° C. The dispersion was stirred for 30minutes while increasing the dispersion temperature to 50° C. Then, thedispersion temperature set point was lowered to 38° C. and 267.7 g ofdeionized water was added over 20 minutes. The dispersion was stirredfor an additional 45 minutes, another 401.5 g of deionized water wasadded over 25 minutes and the final dispersion stirred for another 45minutes.

[0159] 3211 g of dispersion and 321 g of deionized water weretransferred to a flask equipped with a stirrer, a thermocouple, and aspiral condenser with water recovery receiver. The dispersion was heatedto 60° C. and the methyl isobutyl ketone removed by vacuum distillation.

[0160] The final dispersion had a solids content of 41.2 weight percent(measured for one hour at 110° C.), a Brookfield viscosity of 54.6centipoise using a #2 spindle at 60 rpm, an acid content of 0.134 meqacid/g (determined by titration with methanolic potassium hydroxide), abase content of 0.137 meq base/g (determined by titration with 0.2 N HClin isopropanol), a pH of 8.54 (as determined by a pH meter), a residualmethyl isobutyl ketone content of 0.26 weight percent (as determined bygas chromatography), a number average particle size of 720 angstroms ,and a volume average particle size of 860 angstroms (as determined byHoriba Model LA 900 laser diffraction particle size instrument).

Example 5

[0161] Synthesis of Hydroxy and Blocked Isocyanate Blocked Polyurethanewith Hydroxypivalic Acid

[0162] This example illustrates the preparation of a polyurethanematerial having both hydroxyl and blocked isocyanate functionality butthe isocyanate was blocked with hydroxy pivalic acid.

[0163] A reaction vessel equipped with a stirrer, a thermocouple, acondenser and a nitrogen inlet was charged with 1548.5 g of isophoronediisocyanate, 459.6 g of methyl isobutyl ketone and 0.70 g of dibutyltin dilaurate and heated to 45° C. 83.7 g of trimethylolpropane wasadded and the reaction was allowed to exotherm to 74° C. After coolingthe reaction to 67° C., another 83.7 g of trimethylolpropane was addedto the reaction flask. The temperature of the reaction product increasedto 90° C. The reaction product was allowed to cool to 75° C. After onehour the reaction's isocyanate equivalent weight was 227.7 grams perisocyanate equivalent.

[0164] 15 889.3 g of TERATHANE® 650 was added over one hour followed by135.0 g of methyl isobutyl ketone. After 30 minutes, the reaction'sisocyanate equivalent weight was 403 grams per equivalent. Then 313.2 gof methyl ethyl ketoxime was added over 30 minutes followed by 90.0 g ofmethyl isobutyl ketone, 138.7 g of hydroxypivalic acid (from TCIAmerica, Portland, Oreg.) and 135.0 g of methyl isobutyl ketone. Thereaction was stirred until the isocyanate equivalent weight was 1425grams per equivalent.

[0165] 1292.3 g of this isocyanate prepolymer were charged to a reactionvessel equipped with a stirrer, a thermocouple, a condenser, and anitrogen inlet. With the vessel contents stirring at 500 rpm and at 78°C., 186.0 g of Jeffamine D-2000 was added over two minutes. Afterstirring an additional 15 minutes, 50.0 g of diethanol amine and 15.0 gof methyl isobutyl ketone were added. The reaction temperature increasedto 82° C. The reaction product was stirred until no evidence ofisocyanate was observed by FTIR. Then 1.6 g of Tinuvin 900, 1.6 g ofTinuvin 123 and 3.2 g of methyl isobutyl ketone were added to thereaction contents.

[0166] The resultant product had an acid value of 12.3 mg KOH/g productand a weight average molecular weight of 5031 g/mole.

Example 6

[0167] Preparation of Aqueous Dispersion of the Hydroxyl and BlockedIsocyanate Polyurethane of Example 5

[0168] 1341.9 g of the polyurethane of Example 5 at 85° C. were addedover 30 minutes to a solution of 623.0 g of deionized water and 26.2 gof dimethyl ethanol amine stirring at 25° C. and at 507 rpm in acylindrical gallon reaction flask equipped with baffles, a doublepitched bladed stirrer, a thermocouple, and a condenser. The dispersiontemperature after this addition was 45° C. The dispersion was stirredfor 30 minutes while increasing the dispersion temperature to 50° C.Then, the dispersion temperature set point was lowered to 38° C. and198.6 g of deionized water was added over 25 minutes. The dispersion wasstirred for an additional 45 minutes, another 546.2 g of deionized waterwas added over 25 minutes and the final dispersion was stirred for anadditional 45 minutes.

[0169] 2655 g of the dispersion were transferred to a flask equippedwith a stirrer, a thermocouple, a Friedrichs condenser, and a receiverflask. The dispersion was heated to 60° C. and the methyl isobutylketone and water removed by vacuum distillation. 118 g of deionizedwater was added to the dispersion.

[0170] The final dispersion had a solids content of 46.8 weight percent(measured for one hour at 110° C.), a Brookfield viscosity of 1440centipoise using a #4 spindle at 12 rpm, an acid content of 0.124 meqacid/g, a base content of 0.125 meq base/g, a pH of 8.50, a residualmethyl isobutyl ketone content of 0.18 weight percent, a number averageparticle size of 4260 angstroms and a volume average particle size of4670 angstroms. Results were obtained using the same testing proceduresdescribed in Example 1.

Example 7

[0171] Preparation of Hydroxy and Blocked Isocyanate Polyurethane UsingDimethylolpropionic Acid (DMPA)

[0172] This example illustrates the preparation of a polyurethanematerial with both hydroxyl and blocked isocyanate functionalitysynthesized using dimethylolpropionic acid as the acid functionality fordispersion rather than trimellitic anhydride used in the above examples.

[0173] A reaction vessel equipped with a stirrer, a thermocouple, acondenser, and a nitrogen inlet was charged with 1697.0 g of isophoronediisocyanate, 484.8 g of methyl isobutyl ketone and 0.74 g of dibutyltin dilaurate and heated to 45° C. 88.4 g of trimethylolpropane wasadded and the reaction was allowed to exotherm to 72° C. After coolingthe reaction to 66° C., another 88.4 g of trimethylolpropane was addedto the reaction flask. The temperature of the reaction product increasedto 89° C. The reaction product was allowed to cool to 75° C. After onehour the isocyanate equivalent weight of the reaction was 207 grams perisocyanate equivalent.

[0174] 938.7 g of TERATHANE® 650 was added over one hour followed by142.5 g of methyl isobutyl ketone. After 30 minutes, the reaction'sisocyanate equivalent weight was 403. Then, 293.9 g of methyl ethylketoxime was added over 30 minutes followed by 95.0 g of methyl isobutylketone, 166.3 g of dimethylolpropionic acid and 142.5 g of methylisobutyl ketone. The reaction was stirred until the isocyanateequivalent weight was 1600 grams per equivalent.

[0175] 1306.7 g of this isocyanate prepolymer were charged to a reactionvessel equipped with a stirrer, a thermocouple, a condenser, and anitrogen inlet. With the vessel contents stirring at 500 rpm and at 70°C., 181.2 g of Jeffamine D-2000 was added over two minutes. Afterstirring an additional 15 minutes, 59.5 g of diethanol amine and 15.0 gof methyl isobutyl ketone were added. The temperature of the reactionproduct increased to 81° C. The reaction product was stirred until noevidence of isocyanate was observed by FTIR.

[0176] The resultant product an acid value of 14.2 mg KOH/g product, ahydroxyl value of 43.2 mg KOH/g product and a weight average molecularweight of 7237 g/mole.

Example 8

[0177] Preparation of Aqueous Dispersion of the Hydroxyl and BlockedIsocyanate Polyurethane of Example 7

[0178] 1341.9 g of the polyurethane of Example 7 at 85° C. were addedover 30 minutes to a solution of 623.0 g of deionized water and 21.2 gof dimethyl ethanol amine stirring at 21° C. and at 529 rpm in acylindrical gallon reaction flask equipped with baffles, a doublepitched bladed stirrer, a thermocouple, and a condenser. The dispersiontemperature after this addition was 45° C. The dispersion was stirredfor 30 minutes while increasing the dispersion temperature to 50° C.Then, the dispersion temperature set point was lowered to 38° C and198.6 g of deionized water was added over 25 minutes. The dispersion wasstirred for an additional 45 minutes, another 546.2 g of deionized waterwas added over 25 minutes and the dispersion stirred for another 45minutes. Then an additional 390.1 g of deionized water was added over 25minutes and the final dispersion stirred for another 45 minutes.

[0179] 3040 g of the dispersion were transferred to a flask equippedwith a stirrer, a thermocouple, a Friedrichs condenser, and a receiverflask. The dispersion was heated to 60° C. and the methyl isobutylketone and water removed by vacuum distillation. This initial dispersionwas not stable, therefore additional dimethyl ethanol amine was added toincrease the percent neutralization to 80 percent.

[0180] The final dispersion had a solids content of 36.3 weight percent(measured for one hour at 110° C.), a Brookfield viscosity of 12,000centipoise using a #3 spindle at 6 rpm, an acid content of 0.112 meqacid/g, a base content of 0.093 meq base/g, a residual methyl isobutylketone content of 0.57 weight percent, a number average particle size of1143 angstroms and a volume average particle size of 1327 angstroms.Results were obtained using the same testing procedures described inExample 1.

[0181] Coating compositions were prepared using the aqueous dispersionsof the above Examples. First, a pigment paste was prepared as follows:EXAMPLE 9: Preparation of Pigment Paste Using Polyurethane Material ofExample 2 A black pigment paste was prepared from the followingingredients: ITEM # COMPONENT Weight in grams 1 Example #2 PolyurethaneMaterial 579.1  2 Nonionic Surfactant¹ 37.0 3 Deionized Water 50.0 4Carbon Black² 65.0 5 Barytes³ 915.0  6 Titanium Dioxide⁴ 20.0 7Deionized Water 42.0 TOTALS 1708.1 

[0182] The first three ingredients were stirred together in the givenorder. The pigments (Items 4, 5 and 6) were added in small portionswhile stirring until a smooth paste was formed. The paste was thenrecirculated for 20 minutes through an Eiger Minimill at 2500 rpm with 2mm zircoa beads. The final product had a Hegman rating of 7.5+. EXAMPLE10: Primer Coating Composition Using Polyurethane of Example 2 A primercoating composition was made by mixing in order the followingingredients: ITEM # COMPONENT Weight in grams 1 Example #9 pigment paste 341.6 2 Example #2 polyurethane 1538.8 material 3 Deionized Water  75.0TOTALS 1955.4

[0183] The pH of the coating was greater than 8.0. The viscosity was 30seconds as measured on a #4 Ford efflux cup at ambient temperature.

[0184] The primer coating composition of this example (Sample A) wasevaluated against a solventborne primer/surfacer (commercially availablefrom PPG Industries Lacke GmbH as PPG-73277) (Comparative Sample). Thetest substrates were ACT cold roll steel panels electrocoated with acationically electrodepositable primer commercially available from PPGIndustries, Inc. as ED-5000, which are commercially available from ACTLaboratories of Hillsdale, Mich. Both the primer coating composition ofthe present invention and the commercial primer/surfacer were sprayapplied (2 coats automated spray with 60 seconds ambient flash betweencoats) at 60% relative humidity and 21° C. to give a dry film thicknessof 1.35 to 1.45 mils (33 microns to 36 microns). The panels were flashedfor 10 minutes at the ambient condition, and were then baked for 10minutes at 80° C. and then 30 minutes at 165° C. The panels weretopcoated with a silver basecoat and flashed for 5 minutes at theambient conditions, and baked for 10 minutes at 80° C. to give a filmthickness of 0.55 to 0.65 mils. The basecoat formulation used is soldunder the tradename HWB519F, commercially available from PPG Industries,Inc., Pittsburgh, Pa.

[0185] The panels were then clearcoated with a 2K clearcoat(commercially available from PPG Industries Cleveland as Part ATKV1050AR/Part B WTKR2000B) and flashed for 10 minutes at ambientcondition and then baked for 30 minutes at 165° C. The thickness of theclearcoat was determined to be 1.8 mils (40 microns).

[0186] The appearance and physical properties of the coated panels weremeasured using the following tests: Chip resistance (multichip) wasmeasured by the Erichsen chip method (PPG STM-0802 or Ford Test Method#BI 157-06, without steps 3 and 4, 2×2000 g, 30 psi) with a rating ofzero being best. Multichip by the GM Gravelometer (PPG STM-0744, or GMTest Method #GME 60-268, −20° C.) with a rating scale of 0-10 with 10being the best. Monochip testing on the BYK-Gardner Monochip Tester (PPGSTM-0823, or BMW Test Method BMW-PA15-163L, RT and −20° C.) with arating of mm of pick-off from the point of impact. By “pick-off” what ismeant is the amount of delamination pulled from the sample by anadhesive. The test results are set forth below in Table 1. TABLE 1 GMGravelometer Chips Rating to metal Monochip −20 ° −20 ° Erichson −20 °Primer RT C. RT C. 1 × 2000 RT C. Compar- 9 2 2 5 2.5 3 (M) 3 (M) ativeSample A 8 8 1 3 1.0 <1 (NF)   2.5 (M)

[0187] As shown in Table 1, the substrate coated with the primer of thepresent invention (Sample A) exhibited generally better chip resistancethan the comparative solventborne commercially available primer surfacer(Comparative Sample).

[0188] Appearance was also measured on the finished panels. Appearancewas measured using the BYK-wavescan (commercially available fromBYK-Gardner, Columbia, Md.) with data collected on the longwave andshortwave numbers. The instrument optically scans the wavy, light darkpattern on the surface over a distance of 10 cm (4 in) and detects thereflected light intensity point by point. The measured optical profileis divided into long-term waviness (structure size 0.6-10 mm) andshort-term waviness (structure size 0.1-0.6 mm). Wavy structures withsizes between 0.1 mm and 10 mm are considered as orange peel ormicrowaviness. Orange peel is observed as a wavy, light-dark pattern ona high gloss surface. The type of structures that can be seen isdependent on the observation distance: long-term waviness at distancesof 2 to 3 m and short-term waviness at about 50 cm (original adhesion,using ASTM # D3359-97). Adhesion was tested by making a crosshatch gridand applying tape (Scotch 610) over the grid. The tape is then pulledfrom the grid and examined for delamination. These results are listed inTable 2. TABLE 2 BYK-wavescan BYK-wavescan X-hatch Sample ShortwaveLongwave Adhesion Comparative 21.7 3.6 Pass Sample A 26.0 5.1 Pass

[0189] The crosshatch samples were then put into a humidity chamber (38°C., 100 percent relative humidity) for ten days (Chrysler Humidity Box)and tested again for adhesion in the same manner listed above. Bothsamples still past this test (i.e. there was no loss of adhesion).

[0190] Example 10 (Sample A) was also applied via automated spray asdescribed above, to precoated line steel (USS Galvaneal) coated withabout 3-4 micrometers of Bonazinc 3001 zinc-rich epoxy pretreatment,which is commercially available from PPG Industries, Inc., Pittsburgh,Pa. This substrate was not electrocoated. The same basecoat andclearcoat described above were applied in a similar manner. The panelswere tested along with the previously reported samples and in the samemanner. The results set forth in Table 3 were observed: TABLE 3 BYKWavescan Erichson Monochip Primer Longwave Shortwave 2 × 2000 R.T. −20Sample A 12.8 35.1 1.0 <1 (NF) 1 (NF) Over Steel Coated with BONAZINC3001

[0191] Example 11: Primer Coating Composition Including Polyurethane ofExample 8 A primer coating composition was made by mixing in order thefollowing ingredients: ITEM # COMPONENT Weight in Grams 1 DeionizedWater 10.7  2 Ethylene Glycol Monobutyl Ether⁵ 1.9 3 NonionicSurfactant¹ 0.6 4 Defoamer⁶ 0.2 5 Carbon Black² 1.3 6 MagnesiumSilicate⁷ 2.5 7 Silicon Dioxide⁸ 0.3 8 Barium Sulfate⁹ 15.5  9 TitaniumDioxide⁴ 0.4 10 Example #8 Polyurethane Material 275.5  11 DeionizedWater 25.0  TOTALS 333.9 

[0192] The first four ingredients were stirred together in the givenorder. The pigments (Items 5-9) were added in small portions whilestirring until a smooth paste was formed. The paste was thenrecirculated for twenty minutes through an Eiger Minimill at 2500 rpmwith 2 mm zircoa beads. The final product had a Hegman rating of 7.5+.The composition of Example 8 and deionized water were added to theproduct in the amounts identified above and stirred. Final viscosity ofthe material was 31 seconds measured using a #4 Ford efflux cup atambient temperature. The pH of the material was measured to be greaterthan 8.0.

[0193] Both of the primer coating compositions of Example 10 and Example11 were spray applied (2 coats automated spray with 60 seconds ambientflash between coats) at 60% relative humidity and 21° C. over Tedlar™, apolyvinyl fluoride film available from DuPont de Nemours Company,Wilmington, Del., (taped to a steel panel and baked at 320° F. for 20minutes) to give a dry film having a thickness of 1.35 to 1.45 mils. Thepanels were flashed for 10 minutes at the ambient condition, and werethen baked for 10 minutes at 80° C. and 30 minutes at 165° C.

[0194] The two primer examples were then tested for determination ofphysical properties. Free films peeled from the coated Tedlar substratewere cut into ½×4″ test strips and were tested for Young's Modulus,tensile strength, percent elongation, and toughness using an InstronMini 44, using a 1″ gauge length and a crosshead speed of 25.4 mm/minute(according to TOUGHNESS TEST METHOD at 25° C.). Results are listed inTable 4. TABLE 4 Sample Young's Modulus Tensile Strength % Toughness ID(MPa) (MPa) Elongation (MPa) Example 662 26 156 22 #10 Example 842 31  8 2 #11

[0195] Comparing the results of the anionic polyurethane primer coatingof the present invention with the commercial primer coating indicatesthat the coatings of the present invention can display better Young'sModulus, tensile strength, percent elongation, and toughness than thecommercially available coatings.

[0196] Coatings including the polyurethane materials of the presentinvention can provide primer and other coating compositions having oneor more desirable properties, such as chip resistance.

[0197] It will be appreciated by those skilled in the art that changescould be made to the embodiments described above without departing fromthe broad inventive concept thereof. It is understood, therefore, thatthis invention is not limited to the particular embodiments disclosed,but it is intended to cover modifications that are within the spirit andscope of the invention, as defined by the appended claims.

We claim:
 1. An anionic self-crosslinkable polyurethane material, thepolyurethane material having a weight average molecular weight of lessthan 15,000 grams per mole, wherein the polyurethane material, whencured, has a toughness of at least 20 MPa according to TOUGHNESS TESTMETHOD at a temperature of 25° C.
 2. The polyurethane material of claim1, wherein the polyurethane material has a weight average molecularweight ranging from about 3,000 to about 10,000 grams per mole.
 3. Thepolyurethane material of claim 2, wherein the polyurethane material hasa weight average molecular weight ranging from about 4,000 to about8,000 grams per mole.
 4. The polyurethane material of claim 1, whereinthe polyurethane material has a combined urethane/urea equivalent weightranging from about 200 to about 400 grams per equivalent.
 5. Thepolyurethane material of claim 1, wherein the polyurethane material hasa combined urethane/urea equivalent weight ranging from about 220 toabout 320 grams of film per urethane group equivalent.
 6. Thepolyurethane material of claim 1, wherein the polyurethane material,when cured, has a toughness ranging from about 20 to about 60 MPaaccording to TOUGHNESS TEST METHOD at a temperature of 25° C.
 7. Thepolyurethane material of claim 6, wherein the polyurethane material,when cured, has a toughness ranging from about 20 to about 50 MPaaccording to TOUGHNESS TEST METHOD at a temperature of 25° C.
 8. Thepolyurethane material of claim 1, wherein the polyurethane materialcomprises isocyanate functional groups, the isocyanate functional groupsblocked with a blocking agent.
 9. The polyurethane material of claim 8,wherein the blocking agent is capable of deblocking from the isocyanatefunctional groups at a temperature ranging from about 90 to about 180°C.
 10. The polyurethane material of claim 9, wherein the blocking agentis capable of deblocking from the isocyanate functional groups at atemperature of less than about 160° C.
 11. The polyurethane material ofclaim 1, wherein the polyurethane material is present in an aqueouscomposition in amount ranging from about 10 to about 60 percent byweight based upon the total weight of the aqueous composition.
 12. Thepolyurethane material of claim 11, wherein the polyurethane material ispresent in the aqueous composition in amount ranging from about 40 toabout 55 percent by weight based upon the total weight of the aqueouscomposition.
 13. The polyurethane material of claim 1, wherein thepolyurethane material, when dispersed in an aqueous medium, is anionicand contains salt groups.
 14. The polyurethane material of claim 1,wherein the polyurethane material is formed from components comprising:(a) at least one polyisocyanate; (b) at least one activehydrogen-containing material; (c) at least one material having at leastone primary or secondary amino group and at least one hydroxyl group;and (d) at least one acid functional material or anhydride having afunctional group reactive with isocyanate or hydroxyl groups of othercomponents from which the polyurethane material is formed.
 15. Thepolyurethane material of claim 14, wherein the polyisocyanate isselected from the group consisting of aliphatic polyisocyanates,cycloaliphatic polyisocyanates, araliphatic polyisocyanate, and aromaticpolyisocyanates, and mixtures thereof.
 16. The polyurethane material ofclaim 15, wherein the polyisocyanate is selected from the groupconsisting of isophorone diisocyanate, tetramethyl xylylenediisocyanate, trimethylhexamethylene diisocyanate, hexamethylenediisocyanate, and mixtures thereof.
 17. The polyurethane material ofclaim 16, wherein the polyisocyanate is isophorone diisocyanate.
 18. Thepolyurethane material of claim 14, wherein the polyisocyanate is presentin an amount ranging from about 10 to about 60 weight percent based uponthe total resin solids of components from which the curable polyurethanematerial is formed.
 19. The polyurethane material of claim 14, whereinthe active hydrogen-containing material is a polyol.
 20. Thepolyurethane material of claim 19, wherein the polyol has a weightaverage molecular weight of less than about 3000 grams per mole.
 21. Thepolyurethane material of claim 20, wherein the polyol has a weightaverage molecular weight of at least about 60 grams per mole.
 22. Thepolyurethane material of claim 21, wherein the polyol is selected fromthe group consisting of trimethylolpropane, ditrimethylolpropane,pentaerythritol, trimethylolethane, and mixtures thereof.
 23. Thepolyurethane material of claim 22, wherein the polyol istrimethylolpropane.
 24. The polyurethane material of claim 14, whereinthe polyol is present in an amount ranging from about 2 to about 50weight percent based upon the total resin solids of components fromwhich the curable polyurethane material is formed.
 25. The polyurethanematerial of claim 14, wherein the polyisocyanate and the activehydrogen-containing material are pre-reacted to form a polyisocyanatefunctional prepolymer prior to addition of remaining components (c)-(d)used to form the polyurethane material.
 26. The polyurethane material ofclaim 14, further comprising a polyoxyalkylene polyamine that is amaterial different from the active hydrogen-containing material.
 27. Thepolyurethane material of claim 14, further comprising a polyoxyalkylenepolyamine that is selected from the group consisting of polyoxypropylenediamine, polytetramethylene glycol bis(3-aminopropyl(ether)), andmixtures thereof.
 28. The polyurethane material of claim 27, wherein thepolyoxyalkylene polyamine is polyoxypropylene diamine.
 29. Thepolyurethane material of claim 14, wherein the polyoxyalkylene polyamineis present in an amount ranging from about 1 to about 50 weight percentbased upon the total resin solids of components from which the curablepolyurethane material is formed.
 30. The polyurethane material of claim14, wherein component (c) is selected from the group consisting ofdiethanol amine, 2-amino-2-methyl-propanediol, diisopropanolamine, andmixtures thereof.
 31. The polyurethane material of claim 30, whereincomponent (c) is diethanol amine.
 32. The polyurethane material of claim14, wherein component (c) is present in an amount ranging from about 2to about 20 weight percent based upon the total resin solids ofcomponents from which the curable polyurethane material is formed. 33.The polyurethane material of claim 14, wherein component (d) is anorganic compound having an acid anhydride group.
 34. The polyurethanematerial of claim 14, wherein component (d) is selected from the groupconsisting of hydroxy pivalic acid and trimellitic anhydride.
 35. Thepolyurethane material of claim 14, wherein component (d) is present inan amount of at least 2 weight percent based upon the total resin solidsof components from which the curable polyurethane material is formed.36. The polyurethane material of claim 14, wherein the components fromwhich the polyurethane material is formed further comprises at least onepolyoxyalkylene polyol.
 37. The polyurethane material of claim 36,wherein the polyoxyalkylene polyol is selected from the group consistingof polyoxyethylene polyols and polyoxypropylene polyols.
 38. Thepolyurethane material of claim 37, wherein the polyoxyalkylene polyol ispolyoxytetramethylene polyol.
 39. The polyurethane material of claim 36,wherein the polyoxyalkylene polyol has a weight average molecular weightof less than about 3000 grams per mole.
 40. The polyurethane material ofclaim 14, wherein the components from which the polyurethane material isformed further comprise a blocking agent.
 41. The polyurethane materialof claim 40, wherein the blocking agent is selected from the groupconsisting of methyl ethyl ketoxime, dimethyl pyrazole,epsilon-caprolactam, diisopropylamine, dibutylamine, di-tert-butylamine,and mixtures thereof.
 42. The polyurethane material of claim 41, whereinthe blocking agent is selected from the group consisting of methyl ethylketoxime, dimethyl pyrazole, and diisopropylamine.
 43. The polyurethanematerial of claim 14, wherein the components from which the polyurethanematerial is formed further comprise an organic solvent.
 44. Thepolyurethane material of claim 14, wherein the components from which thepolyurethane material is formed further comprise a tertiary amine. 45.The polyurethane material of claim 44, wherein the tertiary amine isdimethylethanol amine.
 46. A powder coating composition comprising thecurable polyurethane material of claim
 1. 47. An aqueous slurry coatingcomposition comprising the curable polyurethane material of claim
 1. 48.A primer coating composition comprising the curable polyurethanematerial of claim
 1. 49. The primer coating composition of claim 48,further comprising a curing agent that is reactive with curable groupsof the polyurethane material.
 50. The primer coating composition ofclaim 48, wherein the polyurethane material is present in the primer inan amount ranging from about 20 to about 100 weight percent based uponthe total resin solids of components from which the primer is formed.51. A basecoat composition comprising the curable polyurethane materialof claim
 1. 52. A clear coating composition comprising the curablepolyurethane material of claim
 1. 53. A monocoat composition comprisingthe curable polyurethane material of claim
 1. 54. A multicomponentcomposite coating comprising a basecoat deposited from a pigmentedcoating composition and a clearcoat applied over the basecoat in whichthe clearcoat is deposited from a clearcoating composition, wherein atleast one of the basecoat composition and the clearcoating compositioncomprise the curable polyurethane material of claim
 1. 55. Amulticomponent composite coating comprising a primer deposited from aprimer coating composition and a topcoat applied over the primer inwhich the topcoat is deposited, wherein at least one of the primercomposition and the topcoat composition comprise the curablepolyurethane material of claim
 1. 56. A coated substrate having coatedlayers applied thereover, at least one of the layers comprising thecurable polyurethane material of claim
 1. 57. An anionicself-crosslinkable polyurethane material, the polyurethane materialhaving a weight average molecular weight of less than 15,000 grams permole, wherein the polyurethane material, when cured, has a toughness ofat least 20 MPa according to TOUGHNESS TEST METHOD at a temperature of25° C., the polyurethane material comprising isocyanate functionalgroups, the isocyanate functional groups blocked with a blocking agent.58. The polyurethane material of claim 57 wherein the polyurethanematerial has a combined urethane/urea equivalent weight ranging fromabout 200 to about 400 grams per equivalent.
 59. The polyurethanematerial of claim 57, wherein the blocking agent is capable ofdeblocking from the isocyanate functional groups at a temperatureranging from about 90 to about 180° C.
 60. A primer compositioncomprising an anionic self-crosslinkable polyurethane material, thepolyurethane material having a weight average molecular weight of lessthan 15,000 grams per mole, wherein the polyurethane material, whencured, has a toughness of at least 20 MPa to TOUGHNESS TEST METHOD at atemperature of 25° C.
 61. The primer composition of claim 60, whereinthe polyurethane material has a combined urethane/urea equivalent weightranging from about 200 to about 400 grams per equivalent.
 62. A processfor forming an aqueous composition comprising a anionicself-crosslinkable polyurethane material, the process comprising: (a)forming the polyurethane material, the polyurethane material having aweight average molecular weight of less than 15,000 grams per mole,wherein the polyurethane material, when cured, has a toughness of atleast 20 MPa according to TOUGHNESS TEST METHOD at a temperature of 25°C.; and (b) dispersing the polyurethane material in water to form anaqueous composition.
 63. The process of claim 62, wherein thepolyurethane material has a combined urethane/urea equivalent weightranging from about 200 to about 400 grams per equivalent.
 64. A processfor preparing a coated substrate, comprising, (a) forming a coating onthe substrate, the coating being a composition comprising an anionicself-crosslinkable polyurethane material, the polyurethane materialhaving a weight average molecular weight of less than 15,000 grams permole, wherein the polyurethane material, when cured, has a toughness ofat least 20 MPa according to TOUGHNESS TEST METHOD at a temperature of25° C.; and (b) at least partially curing the coating.
 65. The processof claim 64, wherein the polyurethane material has a combinedurethane/urea equivalent weight ranging from about 200 to about 400grams per equivalent.